Registration of L‐74X nonshattering basin wildrye × creeping wildrye germplasm

Abstract Basin wildrye [ Leymus cinereus (Scribn. & Merr.) Á. Löve] is somewhat indeterminate and shatters its seed. To avoid shattering losses, growers tend to harvest basin wildrye seed prior to maximal physiological maturity. To resolve the intersecting problems of floral indeterminacy and seed shattering, USDA‐ARS released the L‐74X basin wildrye × creeping wildrye [ L. triticoides (Buckl.) Pilger] germplasm (Reg. no. GP‐106, PI 701909) on August 26, 2021. While L‐74X has a narrow genetic base due to a biparental cross in its history, it can be used to introgress the nonshattering recessive sh6 allele of creeping wildrye (2 n = 4 x = 28) into 4 x basin wildrye and closely related 4 x Leymus species. L‐74X originated with hybridization between 4 x populations of basin wildrye and creeping wildrye, followed by eight generations of recombination and natural selection that restored fertility to the interspecific hybrid. Intentional selection led to fixation of the sh6 allele. Averaged across 2 years, shattering genotypes ( Sh6/sh6 ) averaged 19.4% greater ( P < 0.05) seed yield per spike 23 days after pollination (DAP), but by 95 DAP, nonshattering genotypes ( sh6/sh6 ) averaged 167% greater ( P < 0.05) seed yield per spike. Germination increased from 72.1% at 23 DAP to 86.4% at 95 DAP. The sh6 allele allows seed growers to delay seed harvest until seed is fully ripe, concomitantly reducing shattering losses and improving physiological seed quality.